Abstract: Through an analysis of seven sections, it is concluded that the ill Basin is a rather active down-rifted basin in Carboniferous where there are two types of lithofacies formations-the volcanic extrusive rocks and carbonates, and three facies zones are developed, including eight facies and six subfacies.

Key words: ill Basin, down-rifted basin, Carboniferous, volcanic extrusive rock, carbonate, turbidite